Process of producing nitrosamine additives



June 1966 I B. BERGHAUS ETAL 3,

PROCESS OF PRODUCING NITROSAMINE ADDITIVES Filed Aug. 24, 1964 9INVENTOR Bernhard fiery/mas Maria Slaesc/ze ATTORNEYS United StatesPatent 3,256,169 PROCESS OF PRODUCING NITROSAMINE ADDITIVES BernhardBerghaus, Zurich, and Maria Staesche, Wettingen, Aargau, Switzerland,assignors to Elektrophysikalische Anstalt Bernhard Berghaus, Vaduz,Liechtenstein, a corporation of Liechtenstein Filed Aug. 24, 1964, Ser.No. 391,388 13 Claims. (Cl. 204-177) This application is acontinuation-in-part of application Ser. No. 27,212 filed May 5, 1960now Patent No. 3,152,056 dated October 6, 1964. p

The present invention relates to the synthesis of addition compounds ofnitrogen-hydrogen and nitrosamine and more particularly to such asynthesis by means of an electric jet discharge.

So far, addition complexes of nitrogen-hydrogen compounds withnitrosamine, such as nitrosamine-hydrazineammonia additives andnitrosamine-ammonia additives, have not had any previous commercialapplication. It has now been found that such nitrosamine additives areparticularly well suited as initial or basic materials for theproduction of hydrazine. Thus the problem which the present inventorsfaced was to find a convenient and advantageous process for preparingsuch nitrosamine addition compounds.

In the process according to the present invention for the preparation ofnitrosamine addition compounds, a gas comprising nitrogen and hydrogenand consisting of one or more gases of the group ammonia, nitrogen andhydrogen, preferably ammonia alone, and a further reactant comprisingoxygen or nitric oxide, is conducted through a jetlike glow discharge,and the reaction products subsequently are separated, preferably withthe aid of a coolant trap in which the nitrosamine additives accumulate.

Suitably the reactants are fed through a nozzle into a reaction vessel,and the jetlike glow discharge is produced in the gas jet issuing fromthe nozzle. The latter preferably is connected as an electrode of theglow discharge, suitably as the cathode. Further, the process suitablyis carried out in a reaction vessel with one or more annular electrodesof which preferably at least one is operated as an anode of the glowdischarge. Moreover, it is of advantage in most cases to use for thegeneration of the jetlike glow discharge a reaction vessel in protectedby protective gaps or slits from the destructive effect of thedischarge.

The glow discharge suitably is effected at a gas pressure from onemillimeter Hg to 30 millimeters Hg, preferably from 2 to 6 millimetersHg. Further, the glow discharge preferably is carried out at voltagesfrom 150 to 400 v. Liquid air or liquid nitrogen preferably is used forcooling the coolant trap.

The invention will be described in greater detail with the aid of theapparatus for carrying out the present process as shown in theaccompanying figure which is a schematic representation of a suitablejet discharge reaction chamber andaccompanying apparatus.

In the apparatus shown, the reaction chamber 1 is enclosed on all sidesby metallic walls 2 that are formed as double walls adapted to receiveand conduct a cooling current in direction of the arrow 3 through theintermediate space 4. The chamber v1 is hermetically closed at its topby a cover 5 composed of electrically insulating material. The covercarries a metallic annular feeding means 6 of which the interior duct 7opens into the chamber 1 through a terminating nozzle 8. The

3,256,169 Patented June 14, 1966 wall enclosing the duct 7 and thenozzle 8 is provided with cooling ducts 9 and 10 through which flows acoolant such as water or liquid air in the direction from inlet 11 tooutlet 12. The points of transition from metal to insulating material onthe cover 5 are protected, in

' a manner known per se, by gaps or slits 13 and 14.

Before that portion of the metallic feeding means 6 and nozzle 8 whichprotrudes into the discharge chamber 1, is produced an electric field,for which purpose a ring 1511- is perpendicularly disposed ascounterelectrode immediately in front of the mouth of nozzle 8, whichring is adjustable along the nozzle axis and is held by the interiorconductor of the insulated bushing 17a. The clear diameter of ring 15a,which is coaxial to the nozzle axis, suffices not to foul the gas jetissuing from the nozzle. The ring 15a is connected via a switch 16a toone pole of a voltage source 18 of which the other pole is connected tosaid means 6 via switch 16. A direct voltage source 18 is preferablyutilized of which the negative pole supplies said means 6 via switch 16.O the other hand, one pole of a voltage source 19, for example fordirect voltage, is connected to switch 16a, and the center tap of saidsource is connected via a switch 16b and a bushing 17b to ring 15b,while the other pole thereof is connected to ring via a switch 16c and abushing 17c. It has proven of advantage to have electrode 15b positivewith respect to electrode 15a.

To said means 6 are fed, perhaps together with a carrier gas and theinitial reactants through the pipe 21 which maybe cut off by a valve 20.If required, the initial reactants may be mixed in advance in the mixer22. The pressure P may be read from a manometer 26. To the lower end ofchamber 1 is connected an outlet line 27 that extends via a shut-offvalve 28 to an absorption assembly 29a and a pump unit 29. The latter isso dimensioned that in chamber 1 at the mouth of line 27 'may bemaintained a predetermined. pressure P that is readable from a pressuregage 34. The pressure ratio P :P shall be increasable to high values.

The nitrosamine addition compound accumulates in the absorption assembly29:: which is a cooling trap cooled by liquid air or other suitablemeans not shown.

I An essential feature of the present process is the maintenance of ajetlike' glow discharge 36 in reaction chamber 1. For such purposesuitably a'pressure of 1 to 30 millimeters mercury, preferably from 2 to6 Hg, is produced in chamber 1 and maintained at least in the immediatevicinity of the mouth of line 27, and at the same time a gas streamunder the pressure P is supplied to chamber 1 through the nozzlelikeopening 8 in said means 6. By properly adjusting the pressure P at themouth of nozzle 8, the clear width thereof and the pump throughput online 27, a steady state is attained in which there is a pressuredifierence (P P in the reaction chamber between the mouth of nozzle 8and the outlet line 27. The entering gas stream adjacent to the mouth ofnozzle 8 assumes the shape of a gas jet, suchv shape being differentdepending on the nozzle form; In FIG. 1 the jet, which is spheroidalwith respect to the nozzle axis, is schematically indicated by thedotted lines 36, the radial extent of the spindle-shaped boundarysurfaces being, however, exaggerated for a better understanding. .Forthe same reason, the jet deformations arising directly at the month arenot shown.

When the gas stream in chamber 1 spreads unhindered, the individual gasparticles will pass at high velocity over the greatest portion of thedistance between nozzle mouth 8 and the counterelectrodes 15. Bysuit-able selection of the total pressure drop (P -P the velocity andthus the flow time of the reactants is adjustable to the desired valuein wide limits.

. Within the jet there develops fromthe usual glow phenomenon on thecathode, a sort of luminescence, mostly in the form of a luminous ray,which with respect to its structure is different from all the phenomenaof gas and glow discharges known so far. The appearance and shape of theluminscent zone apparently is defined by the gas jet, .but occasionallya Stratification is noticeable within the luminescence. The spectralrange of the light emission is set, within a certain range, by thereactions taking place in the jet. The light-emitting regions inside thejet are not, of course, the only portions that enter into question forthe present purpose of carrying out reactions, rather the reaction zoneproper may comprise also nonluminous jet portions as well as theimmediate vicinity thereof and may extend into the nozzle opening 8.

The shape of the reaction zone is determined to a large extent by theflow velocity of the jet, although the reaction zone does not have toextend entirely across the jet. An essential feature of the present formof discharge is the sharp demarcation thereof with respect to itsvicinity, which would seem to depend on the steep pressure drop from thejet interior to the rim thereof. As, in accordance with a knownconformity, the energy exchange of gas discharge rises according to anapproximately cubic function with the gas pressure, and since, there isalready a pressure P at the rim of the vessel, the reaction appears tobe most intense inside the jet where at the same time prevails a maximumion density at a relatively low temperature. The reactants, according toall experience, are already dissociated by the electric action shortlyafter leaving nozzle 8. When passing through the high ion density of jet36, the reaction of the individual ions occurs.

The length of time during which the reactants remain in the jet, isnormally in the order of fractions of milliseconds to fractions ofseconds. Such short and adjustable duration of action and the abovementioned fact that the reactants leaving the jet arrive at once in aspace portion of different pressure, another concentration and 'anothertemperature, is considered the cause of the surprising chemical effectof the present process.

When supplying ammonia and oxygen in excess through nozzle 8 into theapparatus, products of light to deep blue are obtained when freezing thereaction products with the aid of liquid air. When thawing theseproducts at temperatures from -110 to 100 C., they melt to a deep-redliquid under vigorous gas discharge.

When further heating said liquid, it emits only slight gas quantities,and the color of the liquid gradually brightens and is a light yellow atabout l C. The heating curve of the liquid extends from thawing (from110 to 100 C.) to room temperature quite uniformly, without stops ordiscontinuities. It follows, therefrom, that the liquid comprises auniform compound and not a mixture of different substances, and neitherare there any rearrangements of this liquid-forming compound within thetemperature range from 100 to +20 C., for on presence of a mixture therewould be stops or constant levels at the temperatures of distillation ofthe various mixture components, while in the case of rearrangementsthere would be discontinuities in the heating curve.

The liquid, therefore, has the same composition at any temperatureWithin this temperature range, and a sample for analyzing the liquid maybe taken at any temperature within said range.

In the present case, a sample for analysis was taken at 10 C., and nofree ammonia was found therein. The sample had an alkaline reaction witha high iodine consumption, the reaction to hydrazine withp-dirnethylaminobenzaldehyde was positive in fresh solution, butregressed quickly. However, the iodine consumption does not similarlydecrease. The liquid evaporates in a few weeks when allowing it tostand, a high gas pressure arising in closed vessels. The liquidcomprises a nitrosamine-ammonia additive of the type where a, b and cintegers.

The invention is illustrated, but not limited, by the following specificexamples:

EXAMPLE 1 10 liters NH were mixed with 13 liters O and introducedthrough nozzle 8 into the reaction chamber. At 185 volts and 104 watts,the pressure P was between 15 and 5 mm. Hg. A linden greenish jet wasformed which below the anode changed to green with blue and, on thebottom of the vessel, to green with yellow.

8.76 grams of a deep-blue substance were frozen, which on thawing at 110C. suddenly ran together to a red liquid containing nitrosamine NH NOWhile a gas escaped. Upon further heating to more than 10 C., said redliquid yielded 6.16 grams of a slightly yellow liquid while emitting asmall volume of gas. This latter liquid did not comprise any freeammonia, had a strong alkaline reaction and a high consumption ofiodine. It showed a reaction to indicate hydrazine in the fresh stateonly. On letting the liquid stand at room temperature, it developedrelatively large quantities of gas and evaporated entirely after a fewweeks.

EXAMPLE 2 By introducing 4 parts by volume of ammonia and one part byvolume of nitric oxide through nozzle 8 into the apparatus describedwith a gas throughput of 3 liters per minute, a pressure of to mm., avoltage from 200 to 340 v. and at 300 to 400 w. power, 18 gms. of adeep-blue product is obtained when freezing the reaction products withliquid air, which product on thawing at about C. also will melt to adeep-red liquid that upon further heating will emit small quantities ofgas and of which the color will gradually brighten. At approximately -l0C. the color of the liquid is a yellowish red. The heating curve of theliquid is also continuous and without stops. Free ammonia was notpresent in a sample taken at 10 C. The liquid comprises anitrosamine-ammonia additive of the formula in which b is very small inrespect to a and c and at the limit mayapproach zero. The sample withp-dimethylaminobenzaldehyde does not react to indicate hydrazine, but ondetermining the ammonia content, the nitrosamine content and thenitrogen content of the sample, there will be found yet very smallquantities of hydrazine, in addition to nitrosamine and amomnia. Fromthis it follows that the actual nitrogen content in most cases issomewhat higher than the nitrogen content calculated from thenitrosamine content and the ammonia content.

EXAMPLE 3 26 liters of a mixture of ammonia gas NH and nitric oxide N0in a volumetric ratio 1:1 were conducted through nozzle 8 into thereaction chamber within 230 seconds. At v. and 19.2 w. the gas pressurein the reaction chamber was between 8 and 2 mm. Hg. There was formed areddish yellow jet issuing from the nozzle, of which the color merged toblue below the anode ring.

7.86 grams of a deep-blue substance was frozen, which ran together at--110 C. to a deep-red liquid while emitting a relatively large quantityof gas. On further heating, the liquid only emitted small quantities ofgas yet and gradually changed its'color to a bright red and orange and,finally at -10 C., to a yellowish red. A sample taken at 10 C. contained41% by weight of ammonia and 59% of nitrosamine NH NO, the ammonia beingadded to the nitrosamine. The sample did not contain any free ammoniaand neither showed any reaction to hydrazine withp-dimethylaminobenzaldehyde.

But said liquid which is red at very low temperatures and which turnsyellow upon heating, also is obtained with mixtures of at least two ofthe substances ammonia, nitrogen, and hydrogen, with oxygen or nitricoxide, or a mixture of the two latter substances. This liquid reactssimilarly as in the cited examples and comprises an additive of the typea(NH -NO)'b(N H -NH )-c(NH a, b and c being integers, whereby at thelimit b may approach zero.

The liquid forming the reaction product, which is red and turns yellowupon heating, by means of finely dispersed metal such as Rainey-nickelmay in all cases be reduced to a substance that contains relativelylarge parts of hydrazine. Particularly good results were obtained by thereduction of a liquid jet discharge reaction product of ammonia andnitric oxide to which at approxi- 'rnately 100 C. were added finelydivided Raincy-nickel.

The reduced liquid showed a preponderant part of hydrazine.

With reference to the three examples described may be remarked that inindustrial production that portion of the gases introduced into thereaction vessel which is not consumed in the formation of the reactionproduct, may again be added, of course, to the process cycle whilecorrespondingly adding the used-up gas quantities. In a continualprocess in accordance with the present invention therefore, only so muchsubstance has to be introduced into the process as has been withdrawnfrom the cycle in the form of reaction product.

It is to be understood, of course, that the foregoing disclosure relatesonly to preferred embodiments of the invention and that numerousmodifications, additions and alterations may be made therein withoutdeparting from the spirit and scope of the invention as set forth in theappended claims.

What we claim is:

1. A process for the production of an addition com pound of nitrosamineand nitrogen hydrogen compounds comprising subjecting a member selectedfrom the group consisting of (l) ammonia gas and (2) at least two gasesof the group consisting of ammonia gas, nitrogen and hydrogen and areactant selected from the group consisting of oxygen and nitrogen oxideto the action of an electric glow discharge in the form of a jetdischarge to form said additions compounds and separating the reactionmixture.

2. A process according to claim 1 in which the reaction is conductedunder a pressure from about-1 to mm. Hg.

3. A process according to claim 2 in which the pressure is about 2 to 6mm. Hg.

4. A process according to claim 1 in which the potential difference atthe power source for the discharge is from to 400 volts.

5. A process according to claim 4 in which the potential dilference isfrom to volts.

. mixture is recovered by freezing.

7. A process according to claim 6 in which the freezing of the reactionmixture is effected by liquid air.

8. A process according to claim 1 in which the nitrogenhydrogencompounds are selected from the group consisting of hydrazine andammonia.

9. A process according to claim 1 in which the reactants are ammonia gasand nitric oxide in a volumetric amount from 4 parts of ammonia to 1part of ammonia per volume of nitric oxide.

10. A process according to claim 1 in which a slight volumetric excessof oxygen is reacted with ammonia.

11. A process for the production of an addition compound of nitrosamineand at least one member of the group consisting of ammonia and hydrazinecomprising introducing at high velocity under pressure through ametallic nozzle shaped restricted inlet into a reaction zone at reducedpressure a member selected from the group consisting of (1) ammonia gasand (2) at least two gases containing said addition compound; removingthe formedreaction mixture rapidly from said zone and separating saidaddition compound from the withdrawn reaction mixture.

12. A process according to claim 11 in which the restricted-inlet has aclear width of about 1 mm.

13. A process according to claim 11 wherein the metallic nozzleelectrode is cathodic.

References Cited by the Examiner UNITED STATES PATENTS 3,003,061 10/1961I Berghaus et al 204-1312 3,020,223 2/1962 Manion 204-177 OTHERREFERENCES Journal of Physical Chemistry, Vol. XXXVH, No. 7,

JOHN H. MACK, Primary Examiner.

HOWARD S. WILLIAMS, Examiner.

1. A PROCESS FOR THE PRODUCTION OF AN ADDITION COMPOUND OF NITROSAMINEAND NITROGEN-HYDROGEN COMPOUNDS COMPRISING SUBJECTING A MEMBER SELECTEDFROM THE GROUP CONSISTING OF (1) AMMONIA GAS AND (2) AT LEAST TWO GASESOF THE GROUP CONSISTING OF AMMONIA GAS, NITROGEN AND HYDROGEN AND AREACTANT SELECTED FROM THE GROUP CONSISTING OF OXYGEN AND NITROGEN OXIDETO THE ACTION OF AN ELECTRIC GLOW DISCHARGE IN THE FORM OF A JETDISCHARGE TO FORM SAID ADDITIONS COMPOUNDS AND SEPARATING THE REACTIONMIXTURE.